The present invention relates to the treatment of impotence in males, enhancement of sexual arousal in females and devices for delivering pharmaceutical compositions to treat impotence in males and sexually stimulate females. In particular, the invention relates to the use of prostaglandin PGE.sub.1 or PGE.sub.2 in combination with PGF.sub.2.alpha. in the treatment of sexual dysfunction.
In excess of about 10 million men in the United States alone exhibit sufficient erectile dysfunction that they can be characterized as effectively impotent. A significant number of men additionally suffer from an inability to develop an erection which may not meet the clinical definition of impotence but may not be satisfactory to their desires or those of their partner to provide mutually satisfactory sexual intercourse. Impotence in the human male can arise from a variety of psychological and physiological etiologies. For example, long term diabetes, damage to the spinal cord, multiple sclerosis, or nerve damage resulting for example from lower abdomen or prostate surgery, and advancing age can result in impotence. Additionally, there are psychological causes for impotence. For differing reasons, each of the foregoing result in an inability to pressurize the corpora cavernosa. which can result in turn from either an insufficient arterial inflow on the supply side, or an insufficient increase in the venous output resistance to blood flow.
A wide variety of mechanical means have been provided, in an effort to overcome erectile dysfunction. For example, U.S. Pat. No. 4,596,242 to Fischell discloses a surgically implantable hydraulic system, having a fluid reservoir and pressure generator, a patient manipulable valve, a pressure reservoir and a distensible member responsive to actuation of the valve. A variety of other prior art mechanical implants and other devices for this purpose are described in the Background of the Invention section of the U.S. Pat. No. 4,596,242.
In addition to the mechanical efforts to overcome erectile dysfunction, pharmaceutical approaches have been tried as well. For example, prostaglandin E.sub.1 has been observed to produce erection in some cases, by direct percutaneous injection into the penis or as a meltable pellet placed in the urethra (U.S. Pat. Nos. 5,773,020; 5,474,535; 5,242,391). PGE.sub.1, in a drug composition known as "trimix", has also been injected directly into the corpus cavemosa to treat impotence. One of the additional ingredients in trimix to phentolamine mesylate.
Most recently Pfizer has made sildenafil citrate available in oral dosages as a treatment for impotence under the trade name, Viagra.RTM.. However, Viagra.RTM. is counter indicated for use by men with cardiac disease, death in cardiac patients during or following intercourse has been indicated as a possible side effect, and interaction with nitroglycerine may cause immediate death. In addition, a new warning has been added to labeling for Viagra.RTM. warning of a possible occurrence of priapism. Also since sildenafil citrate is administered orally, the effect of the drug is systemic and not restricted, as in direct delivery to the penis, to a localized response.
Further, both PGE.sub.1 and Viagra.RTM. have been shown to be effective in only certain causes of impotence. In particular, neither drug appears to be particularly effective to treat impotence resulting from surgical procedures on the prostate.
Still further, the needs for localized drugs to treat female sexual deficiencies have not been adequately addressed by presently available products. It is estimated that there are ten million women in the United States who suffer from female sexual arousal dysfunction.
Therefore, there remains a need for an improved treatment of erectile dysfunction in the male and arousal dysfunction in the female. Surgical implantation and/or repeated injections range from disfavored to medically disadvantageous, and do not, as a whole, provide a satisfactory solution to the problem. From a patient usability standpoint, erectile dysfunction would most advantageously be treated on a self-administration basis, without the need of surgical intervention or repeated injections of a pharmaceutical agent. This problem has been addressed by the use of PGE.sub.2 as claimed in my U.S. Pat. No. 5,708,031. However, some patients on using urethral placement of PGE.sub.2 materials have experienced urethral burning and cavernous sinus aching within the genital area. This unpleasant sensation is also experienced on use of PGE.sub.1. To counteract this side effect an anesthetic may be added to the prostaglandin formulation. However, this in turn requires using an increased quantity of the prostaglandin.
Further, the prior gel formulation and the PGE.sub.1 pellet requires the delivery of a greater volume of treatment composition than may be desired. Still further, it would be a significant improvement if a simple and safe composition is available for application to the female external genitalia which would increase sensitivity, enhance lubrication and result in local vasodilation and engorgement of external and meatal tissue all of which would enhance the female sexual arousal and experience.
Therefore, there is a need for a PGE.sub.2 formulation which avoids these negative sensations but does not interfere with the effectiveness of the PGE.sub.2 for treatment of impotence.